Wheel bearing device and method for manufacturing said device

ABSTRACT

A wheel bearing device (1) including: an outer member (2) on the inner periphery of which an outer-side rolling surface (2c/2d) is formed; an inner member (3) on the outer periphery of which an inner-side rolling surface (3c/3d) is formed; and a plurality of rolling bodies (41) interposed between the rolling surfaces (2c/2d/3c/3d) of the outer member (2) and the inner member (3). The wheel bearing device having a spline hole (3b) formed in a through hole (3h) of the inner member (3). The spline hole includes a guide groove (3G) formed on an inner circumferential surface thereof. A guide plate (8G) of a finishing broach (8) passes through the guide groove in the inner periphery of the spline hole (3b).

TECHNICAL FIELD

The present invention relates to a wheel bearing device and a method formanufacturing said device.

BACKGROUND ART

Conventionally, there is known a wheel bearing device that rotatablysupports a wheel (for example, see Patent Literature 1 and PatentLiterature 2). The wheel bearing device includes an outer member fixedto a vehicle body. Further, at an inner side of the outer member, aninner member is disposed. The outer member and the inner member eachhave a raceway face. Between the raceway faces, a plurality of rollingelements are interposed. With this configuration, the wheel bearingdevice forms a rolling bearing structure, and rotatably supports thewheel that is attached to the inner member.

Patent Literature 1 discloses a wheel bearing device that includes aninner member including a spline hole, and a universal joint including aspline shaft; and the spline shaft is fitted into the spline hole. Inthe wheel bearing device, the spline hole has, on its surface, an unevenshape that is formed parallel to an axial direction. Thus, when anuneven shape of the spline shaft is circumferentially twisted, atwisting load is applied to the uneven shape of each of the spline holeand the spline shaft. As a result, circumferential looseness is reduced.With such a fitted structure, the spline shaft needs to have, at itstip, a bolt or the like attached. When the spline shaft is inserted intothe spline hole, the bolt or the like attached needs to be turned tofurther pull the spline shaft into the spline hole.

On the other hand, Patent Literature 2 discloses a wheel bearing deviceincluding a spline shaft, a tip of which has no bolt or the likeattached, and the spline shaft is thus not pulled into the spline hole.With the wheel bearing device in this state, the spline shaft, too,needs to have its uneven shape formed parallel to an axial direction,and a certain degree of circumferential looseness needs to be allowed.With such a fitted structure, heat treatment is provided to each of thespline hole and the spline shaft. As a result, the uneven shape of thecorresponding spline hole and the corresponding spline shaft are lessprone to be worn or damaged.

When the heat treatment is provided to the spline hole, the uneven shapeof the spline hole is deformed, degrading initial machining accuracy.Thus, a countermeasure considered is to run a broach through the splinehole again after the heat treatment, and the uneven shape of the splinehole is finished at high accuracy. However, matching a phase of thebroach to the uneven shape of the spline hole is difficult; and in anunmatched state, running the broach through the spline hole may hinderthe spline hole from securing an appropriate cutting allowance and beingfinished at high accuracy. Further, a broached surface may be roughened,and the broach may be overloaded and reduced in service life.

CITATIONS LIST Patent Literature

Patent Literature 1: JP-A 2017-47716 Gazette

Patent Literature 2: JP-A 2011-240755 Gazette

SUMMARY OF INVENTION Technical Problems

The present invention provides a technique to easily match the phase ofthe broach to the uneven shape of the spline hole, and to finish theuneven shape of the spline hole at high accuracy by securing theappropriate cutting allowance. Further, the present invention provides atechnique to protect the broached surface from being roughened, and toprevent the broach from being overloaded and reduced in service life.

Solutions to Problems

A first aspect of the present invention provides a wheel bearing deviceincluding:

an outer member having an outer raceway face that is formed on an innercircumference of the outer member;

an inner member having an inner raceway face that is formed on an outercircumference of the inner member; and

a plurality of rolling elements that are interposed between the outerraceway face of the outer member and the inner raceway face of the innermember.

The wheel bearing device further includes a spline hole that is formedin a through hole of the inner member.

In the wheel bearing device, the spline hole includes a guide groovethat is formed on an inner circumference of the spline hole, the guidegroove through which a guide plate of a finishing broach is to be run.

In a second aspect of the present invention, the wheel bearing deviceaccording to the first aspect of the present invention is configured inthat the guide groove is formed of a plurality of recesses that areadjacent to each other and are circumferentially connected to eachother, the plurality of recesses as a part of recesses that form theuneven shape.

In a third aspect of the present invention, the wheel bearing deviceaccording to the first aspect or the second aspect of the presentinvention is configured in that the inner member includes a phasematching portion that is formed on an inner-side end face of the innermember and recessed at an outer side of the inner member, and the phasematching portion is formed in a shape where an inner-side opening end ofthe guide groove spreads radially outward.

In a fourth aspect of the present invention, the wheel bearing deviceaccording to any one of the first aspect to the third aspect of thepresent invention is configured in that the guide plate includes across-sectional face formed to be inclined toward a side face of theguide groove, and as the guide plate goes into the guide groove, a gapbetween the cross-sectional face of the guide plate and the side face ofthe guide groove is gradually reduced.

A fifth aspect of the present invention provides a method formanufacturing a wheel bearing device,

the wheel bearing device including:

an outer member having an outer raceway face that is formed on an innercircumference of the outer member;

an inner member having an inner raceway face that is formed on an outercircumference of the inner member; and

a plurality of rolling elements that are interposed between the outerraceway face of the outer member and the inner raceway face of the innermember.

The method for manufacturing the wheel bearing device includes:

a forming step of forming a spline hole by running a forming broachthrough a through hole of the inner member;

a heat treatment step of providing a heat treatment to the outer racewayface, the inner raceway face, and the spline hole; and

a finishing step of finishing an uneven shape of the spline hole at highaccuracy by running a finishing broach through the spline hole after theheat treatment step.

In a sixth aspect of the present invention, the method for manufacturingthe wheel bearing device according to the fifth aspect of the presentinvention is configured in that

the finishing step includes a step of fitting a guide plate of thefinishing broach into a guide groove that is formed on an innercircumference of the spline hole.

Advantageous Effects of Invention

In a wheel bearing device according to the first aspect of the presentinvention, a guide groove is formed on an inner circumference of aspline hole, and a guide plate of a finishing broach is to be runthrough the guide groove. In the wheel bearing device, a phase of thefinishing broach is easily matched to an uneven shape of the splinehole. Additionally, it is possible to finish the uneven shape of thespline hole at high accuracy by securing an appropriate cuttingallowance. Further, it is possible to protect a broached surface frombeing roughened, and to prevent the finishing broach from beingoverloaded and reduced in service life.

In a wheel bearing device according to the second aspect of the presentinvention, the guide groove is formed of a plurality of recesses thatare adjacent to each other and are circumferentially connected to eachother. The plurality of recesses are a part of recesses that form theuneven shape. In the wheel bearing device, when the spline hole isformed by running a forming broach, the guide groove is concurrentlyformed. This configuration simplifies a step of manufacturing the wheelbearing device. As a result, it is possible to suppress an increase ofcost.

In a wheel bearing device according to the third aspect of the presentinvention, a phase matching portion is formed in a shape where aninner-side opening end of the guide groove spreads radially outward. Inthe wheel bearing device, an operator grasps a position of the guidegroove at a glance, and thus a step of fitting the guide plate of thefinishing broach into the guide groove is easily performed.

In a wheel bearing device according to the fourth aspect of the presentinvention, the guide plate includes a cross-sectional face formed to beinclined toward a side face of the guide groove. With thisconfiguration, as the guide plate goes into the guide groove, a gapbetween the cross-sectional face of the guide plate and the side face ofthe guide groove is gradually reduced. In the wheel bearing device, theguide plate goes into the guide groove in accordance with an inclinationof the cross-sectional face, and the phase of the finishing broach isthereby tuned.

In a method for manufacturing a wheel bearing device according to thefifth aspect of the present invention, a finishing step is included. Thefinishing step is a step of, after providing a heat treatment to aspline hole, running a finishing broach through the spline hole. In themethod for manufacturing the wheel bearing device, it is possible tofinish an uneven shape of the spline hole at high accuracy.

In a method for manufacturing the wheel bearing device according to thesixth aspect of the present invention, the finishing step includes astep of fitting a guide plate of the finishing broach into a guidegroove that is formed on an inner circumference of the spline hole. Inthe method for manufacturing the wheel bearing device, a phase of thefinishing broach is easily matched to the uneven shape of the splinehole. Additionally, it is possible to finish the uneven shape of thespline hole at high accuracy by securing an appropriate cuttingallowance. Further, it is possible to protect a broached surface frombeing roughened, and to prevent the finishing broach from beingoverloaded and reduced in service life.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a wheel bearing device.

FIG. 2 illustrates a configuration of the wheel bearing device.

FIG. 3 illustrates a part of the configuration of the wheel bearingdevice.

FIG. 4 illustrates a part of the configuration of the wheel bearingdevice.

FIG. 5 shows a step of manufacturing a hub race.

FIG. 6 illustrates a step of forming a spline hole.

FIG. 7 illustrates a guide groove formed on an inner circumference ofthe spline hole.

FIG. 8 illustrates a step of finishing an uneven shape of the splinehole at high accuracy.

FIG. 9(A) illustrates a cutting allowance including a side face to beremoved by a finishing broach.

FIG. 9(B) illustrates a cutting allowance including a side face and anupper face to be removed by a finishing broach.

FIG. 10 illustrates a state where a guide plate goes into the guidegroove.

FIG. 11 illustrates a state where a guide plate according to otherembodiment goes into the guide groove.

FIG. 12 illustrates the finishing broach including a shaft body, the tipof which is formed in a tapered shape.

FIG. 13 illustrates the hub race where a plurality of guide grooves areformed, and the finishing broach where a plurality of guide plates areprovided.

DESCRIPTION OF EMBODIMENTS

First, a wheel bearing device 1 according to the present invention willbe described. FIG. 1 illustrates the wheel bearing device 1. FIG. 2illustrates a configuration of the wheel bearing device 1. FIGS. 3 and 4each illustrate a part of the configuration of the wheel bearing device1.

The wheel bearing device 1 rotatably supports a wheel. The wheel bearingdevice 1 includes an outer member 2, an inner member 3, and two rollingelement rows 4. In this description, an “inner side” represents avehicle body side of the wheel bearing device 1 when attached to avehicle body, and an “outer side” represents a wheel side of the wheelbearing device 1 when attached to the vehicle body. Additionally,“radially outward” represents a direction away from a rotational axis Aof the inner member 3, and “radially inward” represents a directioncloser to the rotational axis A of the inner member 3. Further, “anaxial direction/axially” represents a direction along the rotationalaxis A of the inner member 3.

The outer member 2 forms an outer race part of a rolling bearingstructure. The outer member 2 includes, on an inner circumference of itsinner-side end, a fitting face 2 a. The outer member 2 also includes, onan inner circumference of its outer-side end, a fitting face 2 b. Thefitting face 2 a and the fitting face 2 b are adjacent to an outerraceway face 2 c and an outer raceway face 2 d, respectively, on theinner circumference of the outer member 2. The outer raceway face 2 copposes an inner raceway face 3 c as will be described later. The outerraceway face 2 d opposes an inner raceway face 3 d as will be describedlater. The outer member 2 further include a knuckle flange 2 e thatextends radially outward. The knuckle flange 2 e includes a plurality ofbolt holes 2 f.

The inner member 3 forms an inner race part of the rolling bearingstructure. The inner member 3 includes a hub race 31 and an inner race32.

The hub race 31 includes, from its inner-side end to its axially centerportion, a small-diameter stepped portion 3 a. The small-diameterstepped portion 3 a indicates a portion where an outer diameter of thehub race 31 is reduced, and an outer circumferential face of thesmall-diameter stepped portion 3 a has a cylindrical shape formed aroundthe rotational axis A. The hub race 31 also includes a spline hole 3 bthat penetrates from an inner-side end to an outer-side end of the hubrace 31. The spline hole 3 b is provided at a center of the hub race 31and has, on its surface, an uneven shape that is formed parallel to theaxial direction. The hub race 31 further includes, on its outercircumference, an inner raceway face 3 d. In a state where the hub race31 is disposed at an inner side of the outer member 2, the inner racewayface 3 d opposes the outer raceway face 2 d as previously described. Thehub race 31 further includes a hub flange 3 e that extends radiallyoutward. The hub flange 3 e includes a plurality of bolt holes 3 f, ineach of which a hub bolt 33 is press-fitted.

The inner race 32 includes, on an outer circumference of its inner-sideend, a fitting face 3 g. The inner race 32 also includes, on its outercircumference and adjacent to the fitting face 3 g, the inner racewayface 3 c. The inner race 32 is fitted to the small-diameter steppedportion 3 a of the hub race 31 to form the inner raceway face 3 c on theouter circumference of the hub race 31. In a state where the inner race32 is combined with the hub race 31 and disposed at the inner side ofthe outer member 2, the inner raceway face 3 c opposes the outer racewayface 2 c as previously described.

The rolling element row 4 forms a rolling part of the rolling bearingstructure. The rolling element row 4 at the inner side includes aplurality of rolling elements 41 and a retainer 42. Similarly, therolling element row 4 at the outer side includes a plurality of rollingelements 41 and a retainer 42.

The rolling elements 41 are each held in a circular shape and evenlyspaced by the retainer 42. The rolling elements 41 included in therolling element row 4 at the inner side are rollably interposed betweenthe outer raceway face 2 c of the outer member 2 and the inner racewayface 3 c of the inner member 3 (inner race 32). The rolling elements 41included in the rolling element row 4 at the outer side are rollablyinterposed between the outer raceway face 2 d of the outer member 2 andthe inner raceway face 3 d of the inner member 3 (hub race 31).

The retainer 42 has an annular shape and includes hollows, each evenlyspaced from the other hollow and configured to house the rolling element41. The retainer 42 includes spherical walls, each of which extendsbetween the rolling elements 41 adjoining each other. Two of thespherical walls sandwich each of the rolling elements 41 therebetween tohold the corresponding rolling element 41. With this configuration, theretainer 42 restricts each of the rolling elements 41 from deviating(moving out of position) circumferentially and radially.

The wheel bearing device 1 according to this application furtherincludes an inner-side seal member 5 and an outer-side seal member 6 inorder to seal an annular space S formed between the outer member 2 andthe inner member 3 (the hub race 31 and the inner race 32). Note that,the inner-side seal member 5 and the outer-side seal member 6 havevarious specifications and are not limited to the specificationsdisclosed in this description.

The inner-side seal member 5 includes a slinger 51 and a seal ring 52.The slinger 51 has its axial cross section portion bent into asubstantial L-shape to form a fitting portion 51 a of a cylindricalshape and a side plate portion 51 b of a disk shape, the side plateportion 51 b extending radially outward. Then, the fitting portion 51 ais fitted to the fitting face 3 g of the inner member 3 (the inner race32). On the other hand, the seal ring 52 is formed of an elastic member54, and a core bar 53 to which the elastic member 54 is bonded. The corebar 53 has its axial cross section portion bent into a substantialL-shape to form a fitting portion 53 a of a cylindrical shape and a sideplate portion 53 b of a disk shape, the side plate portion 53 bextending radially inward. Then, the fitting portion 53 a is fitted tothe fitting face 2 a of the outer member 2. The elastic member 54includes two dust lips 54 a and 54 b, each having a tip edge in contactwith the side plate portion 51 b of the slinger 51 that is disposedopposite the two dust lips 54 a and 54 b. The elastic member 54 furtherincludes a grease lip 54 c having a tip edge in contact with or inproximity of the fitting portion 51 a of the slinger 51 that is disposedopposite the grease lip 54 c.

The outer-side seal member 6 is formed of an elastic member 62, and acore bar 61 to which the elastic member 62 is bonded. The core bar 61has its axial cross section portion bent into a substantial L-shape toform a fitting portion 61 a of a cylindrical shape and a side plateportion 61 b of a disk shape, the side plate portion 61 b extendingradially inward. Then, the fitting portion 61 a is fitted to the fittingface 2 b of the outer member 2. The elastic member 62 includes two dustlips 62 a and 62 b, each having a tip edge in contact with acircular-arc face 3 i that is connected to the hub flange 3 e. Theelastic member 62 further includes a grease lip 62 c having a tip edgein contact with or in proximity of a shaft circumferential face 3 j thatis connected to the circular-arc face 3 i.

Next, a step of manufacturing the hub race 31 will be described. FIG. 5shows the step of manufacturing the hub race 31. Here, the descriptionwill focus on a part of the step related to the invention of thisapplication.

In step S1, the spline hole 3 b is formed (forming step). Morespecifically, the hub race 31 includes a through hole 3 h at a center ofthe hub race 31, and in step S1, the spline hole 3 b is formed byrunning a broach 7 through the through hole 3 h (see FIG. 6 ). Notethat, in this description, the broach 7 used in step S1 is defined as a“forming broach 7”.

In step S2, the spline hole 3 b is subjected to heat treatment. In stepS2, in addition to the spline hole 3 b, the outer raceway faces 2 c and2 d as well as the inner raceway faces 3 c and 3 d are subjected to theheat treatment. More specifically, in step S2, a coil body is insertedinto the spline hole 3 b to generate an electric current flow throughthe spline hole 3 b, and an eddy current induces heat. As a result, theheat treatment is provided to the spline hole 3 b. Note that, a hardenedlayer depth has a wave-shape change in accordance with the uneven shapeof the spline hole 3 b (see an area hatched in each of FIGS. 7 and 9 ).The heat treatment is not required of a phase matching portion 3S aswill be described later.

In step S3, the uneven shape of the spline hole 3 b is finished at highaccuracy (finishing step). More specifically, the uneven shape of thespline hole 3 b still has a cutting allowance, and the cutting allowanceis removed by running a broach 8 through the spline hole 3 b. As aresult, the uneven shape of the spline hole 3 b is finished at highaccuracy (see FIG. 8 ). Note that, in this description, the broach 8used in step S3 is defined as a “finishing broach 8”.

Next, the step of forming the spline hole 3 b (forming step) will bedescribed in detail. FIG. 6 illustrates the step of forming the splinehole 3 b. FIG. 7 illustrates a guide groove 3G formed on an innercircumference of the spline hole 3 b.

First, the forming broach 7 will be described. The forming broach 7includes a shaft body 7 a, and a plurality of cutting blades 7 b, eachof which is disposed around the shaft body 7 a. More specifically, theforming broach 7 includes a cutting blade row 7L that is formed of theplurality of cutting blades 7 b disposed in a circumferential directionof the shaft body 7 a. The cutting blade row 7L is axially provided atmultiple stages. The forming broach 7 also includes, at its tip, a grip7 c. Then, the grip 7 c is gripped and pulled by a broaching machine sothat the forming broach 7 is run through the through hole 3 h.

With this configuration, the forming broach 7 is run through the throughhole 3 h of the hub race 31 to cause each of the cutting blades 7 b togradually shave off an inner circumferential face of the through hole 3h. As a result, the spline hole 3 b is formed. The spline hole 3 bformed has the uneven shape where each of recesses 3R (that form theuneven shape) has a side face 3 s formed in an involute curve shape. Inother words, each of projections 3P (that form the uneven shape) has theside face 3 s formed in the involute curve shape.

In the forming broach 7, each of the cutting blades 7 b of the cuttingblade rows 7L is designed to be circumferentially large. The cuttingblades 7 b, each circumferentially large, are disposed in a row along acentral axis B (see a two-dot chain line in FIG. 6 ). An object of thisconfiguration is to form the spline hole 3 b, and concurrently to formthe guide groove 3G that is large in width. Note that, the guide groove3G is not formed in the projections 3P of the uneven shape. The guidegroove 3G is a part where the recesses 3R on both sides of theprojections 3P are circumferentially connected to each other. In otherwords, the guide groove 3G is formed of the plurality of recesses 3Rthat are adjacent to each other and are circumferentially connected toeach other. The guide groove 3G included in the hub race 31 according tothis application is formed of two of the recesses 3R that are adjacentto each other and are circumferentially connected to each other.

As has been described above, the guide groove 3G is formed of the two ofthe recesses 3R adjacent to each other in order to facilitate a guideplate 8G (to be described later) to be fitted into the guide groove 3G.Additionally, this configuration is most appropriate in terms ofrigidity and strength. Here, the guide groove 3G may be formed of one ofthe recesses 3R; however, in this case, the guide plate 8G is less proneto be fitted into the guide groove 3G. The guide groove 3G may also beformed of three or more of the recesses 3R; however, in this case, therigidity and the strength of the guide groove 3G are degraded.Accordingly, the configuration with which the guide groove 3G is formedof the two of the recesses 3R adjacent to each other is considered as atechnical feature.

Next, the step of finishing the uneven shape of the spline hole 3 b athigh accuracy (finishing step) will be described in detail. FIG. 8illustrates the step of finishing the uneven shape of the spline hole 3b at high accuracy. FIG. 9(A) illustrates a cutting allowance Tincluding a side face 3 s to be removed by the finishing broach 8. FIG.9(B) illustrates the cutting allowance T including a side face 3 s andan upper face 3 t to be removed by the finishing broach 8.

First, the finishing broach 8 will be described. The finishing broach 8includes a shaft body 8 a, and a plurality of cutting blades 8 b, eachof which is disposed around the shaft body 8 a. More specifically, thefinishing broach 8 includes a cutting blade row 8L that is formed of theplurality of cutting blades 8 b disposed in a circumferential directionof the shaft body 8 a. The cutting blade row 8L is axially provided atmultiple stages. The finishing broach 8 also includes, at its tip, agrip 8 c. Then, the grip 8 c is gripped and pulled by a broachingmachine so that the finishing broach 8 is run through the spline hole 3b.

With this configuration, the finishing broach 8 is run through thespline hole 3 b of the hub race 31 to cause each of the cutting blades 8b to gradually shave off the uneven shape of the spline hole 3 b. As aresult, the uneven shape of the spline hole 3 b is finished at highaccuracy. The spline hole 3 b finished also has the uneven shape whereeach of the recesses 3R (that form the uneven shape) has a side face 3 sformed in an involute curve shape. In other words, each of projections3P (that form the uneven shape) has the side face 3 s formed in theinvolute curve shape.

In the finishing broach 8, each of the cutting blades 8 b of the cuttingblade rows 8L is designed to be circumferentially large. The cuttingblades 8 b, each circumferentially large, are disposed in a row alongthe central axis B (see a two-dot chain line in FIG. 8 ). An object ofthis configuration is to finish the uneven shape of the spline hole 3 bat high accuracy, and concurrently to form the guide groove 3G that islarge in width at high accuracy. Further, the finishing broach 8includes the guide plate 8G that is formed on an outer circumference ofa tip of the shaft body 8 a and protruded radially outward. The guideplate 8G has a cuboid shape, the lengthwise direction of which extendsalong the central axis B. The guide plate 8G fits into the guide groove3G when the finishing broach 8 is run through the spline hole 3 b.

As has been described above, in the wheel bearing device 1 according tothis application, the guide groove 3G is formed on the innercircumference of the spline hole 3 b, and the guide plate 8G of thefinishing broach 8 is run through the guide groove 3G. With thisconfiguration, it is possible to easily match a phase of the finishingbroach 8 to the uneven shape of the spline hole 3 b. Then, asillustrated in FIG. 9(A), the finishing broach 8 shaves off the sideface 3 s of each of the projections 3P forming the uneven shape.Further, as illustrated in FIG. 9(B), in addition to the side face 3 sof each of the projections 3P forming the uneven shape, the finishingbroach 8 may shave off an upper face 3 t of the corresponding projection3P. Here, a drill may be additionally used to shave off the upper face 3t of the corresponding projection 3P. The cutting allowance T isappropriately 0.2 mm to 0.3 mm.

Next, other features of the wheel bearing device 1 according to thisapplication will be described. FIG. 10 illustrates a state where theguide plate 8G goes into the guide groove 3G. FIG. 11 illustrates astate where a guide plate 8G goes into a guide groove 3G, both accordingto other embodiment.

In the wheel bearing device 1 according to this application, the phasematching portion 3S is formed on an inner-side end face of the hub race31 and recessed at the outer side. The phase matching portion 3S isequal in width to the guide groove 3G, and gradually spreads radiallyoutward as closer to the inner side (see FIG. 10 ). In other words, thephase matching portion 3S is formed in a shape where an inner-sideopening end of the guide groove 3G spreads radially outward. Thisconfiguration causes an operator to grasp a position of the guide groove3G at a glance without looking into the spline hole 3 b. Further, theguide plate 8G goes into the guide groove 3G in accordance with aninclination of the phase matching portion 3S, and thus a step of fittingthe guide plate 8G into the guide groove 3G is easily performed.

In a step of manufacturing the wheel bearing device 1 according to thisapplication, the step of fitting the guide plate 8G of the finishingbroach 8 into the guide groove 3G is important. In order to smoothlyperform the step, the guide plate 8G may be formed in a wedge shape. Inother words, the guide plate 8G may have a cross-sectional face 8 sformed to be inclined toward the side face 3 s of the guide groove 3G.With this configuration, as the guide plate 8G goes into the guidegroove 3G, a gap between the cross-sectional face 8 s of the guide plate8G and the side face 3 s of the guide groove 3G is gradually reduced(see FIG. 11 ). As a result, the guide plate 8G goes into the guidegroove 3G in accordance with the inclination of the cross-sectional face8 s, and thus the step of fitting the guide plate 8G into the guidegroove 3G is easily performed. In this regard, the phase matchingportion 3S may be formed to gradually spread radially as closer to theinner side. Even with this configuration, the guide plate 8G goes intothe guide groove 3G in accordance with the inclination of a side face ofthe phase matching portion 3S, and thus the step of fitting the guideplate 8G into the guide groove 3G is easily performed.

Next, a finishing broach 8 according to the other embodiment will bedescribed. FIG. 12 illustrates the finishing broach 8 including a shaftbody 8 a, the tip of which is formed in a tapered shape. Note that, FIG.12(X) is a sectional view taken along line X-X.

As illustrated in FIG. 12 , in the finishing broach 8 according to thisembodiment, the tip of the shaft body 8 a has its outer diametergradually increasing. Accordingly, when D1 represents the outer diameterat a front end of the tip of the shaft body 8 a, and D2 represents theouter diameter at a rear end of the tip of the shaft body 8 a, arelationship between D1 and D2 is expressed by Mathematical Formula Abelow. Further, when D3 represents a large diameter of each of the guidegroove 3G and a recess 3R (diameter of a circle formed by connecting theguide groove 3G and a bottom face of the recess 3R), a relationshipamong D1, D2, and D3 is expressed by Mathematical Formula B below. Notethat, when the tip of the shaft body 8 a has the tapered shape, across-sectional face 8 s of the guide plate 8G gradually narrows fromits front end and eventually merges into a side face 3 s of a projection3P. With this configuration, the step of fitting the guide plate 8G ofthe finishing broach 8 into the guide groove 3G is performed moresmoothly, and the phase of the finishing broach 8 is more preciselymatched. This configuration also controls eccentricity of the finishingbroach 8.

D1<D2  Mathematical Formula A:

D2≤(D1+D2)/2≤D3  Mathematical Formula B:

Next, a hub race 31 and the finishing broach 8, both according to theother embodiment, will be described. FIG. 13 illustrates the hub race 31where a plurality of guide grooves 3G are formed, and the finishingbroach 8 where a plurality of guide plates 8G are provided.

As illustrated in FIG. 13 , in the hub race 31 according to thisembodiment, the plurality of guide grooves 3G are spaced evenly on aninner circumference of a spline hole 3 b. Each of the guide grooves 3Gaxially extends from three phase matching portions 3S that are similarlyspaced evenly. Concurrently, in the finishing broach 8 according to thisembodiment, the plurality of guide plates 8G are spaced evenly on anouter circumference of the tip of the shaft body 8 a. Each of the guideplates 8G has a cuboid shape, the lengthwise direction of which extendsalong the central axis B, or has a wedge shape. Each of the guide plates8G fits into the corresponding guide groove 3G when the finishing broach8 is run through the spline hole 3 b. With this configuration, a phaseof the finishing broach 8 is more precisely matched. This configurationalso controls eccentricity of the finishing broach 8.

The invention of this application and advantageous effects thereof willbe summarized below.

In a wheel bearing device 1 according to this application, a spline hole3 b has a guide groove 3G that is formed on an inner circumference ofthe spline hole 3 b, and a guide plate 8G of a finishing broach 8 is runthrough the guide groove 3G. In the wheel bearing device 1, a phase ofthe finishing broach 8 is easily matched to an uneven shape of thespline hole 3 b. Additionally, it is possible to finish the uneven shapeof the spline hole 3 b at high accuracy by securing an appropriatecutting allowance T. Further, it is possible to protect a broachedsurface of the spline hole 3 b from being roughened, and to prevent thefinishing broach 8 from being overloaded and reduced in service life.

In the wheel bearing device 1 according to this application, the guidegroove 3G is formed of a plurality of recesses 3R that are adjacent toeach other and are circumferentially connected to each other. Theplurality of recesses 3R are a part of the recesses 3R that form theuneven shape. In the wheel bearing device 1, when the spline hole 3 b isformed by running a forming broach 7, the guide groove 3G isconcurrently formed. This configuration simplifies a step ofmanufacturing the wheel bearing device. As a result, it is possible tosuppress an increase of cost.

In the wheel bearing device 1 according to this application, a phasematching portion 3S is formed in a shape where an inner-side opening endof the guide groove 3G spreads radially outward. In the wheel bearingdevice 1, an operator grasps a position of the guide groove 3G at aglance, and thus a step of fitting the guide plate 8G of the finishingbroach 8 into the guide groove 3G is easily performed.

Further, in the wheel bearing device 1 according to this application,the guide plate 8G has a cross-sectional face 8 s formed to be inclinedtoward a side face 3 s of the guide groove 3G. With this configuration,as the guide plate 8G goes into the guide groove 3G, a gap between thecross-sectional face 8 s of the guide plate 8G and the side face 3 s ofthe guide groove 3G is gradually reduced. In the wheel bearing device 1,the guide plate 8G goes into the guide groove 3G in accordance with aninclination of the cross-sectional face, and the phase of the finishingbroach 8 is thereby tuned.

Additionally, in a method for manufacturing the wheel bearing device 1according to this application, a finishing step includes a step offitting the guide plate 8G of the finishing broach 8 into the guidegroove 3G that is formed on the inner circumference of the spline hole 3b. In the method for manufacturing the wheel bearing device 1, the phaseof the finishing broach 8 is easily matched to the uneven shape of thespline hole 3 b. Additionally, it is possible to finish the uneven shapeof the spline hole 3 b at high accuracy by securing an appropriatecutting allowance T. Further, it is possible to protect a broachedsurface of the spline hole 3 b from being roughened, and to prevent thefinishing broach 8 from being overloaded and reduced in service life.

The wheel bearing device 1 according to this application has a typicallycalled third generation structure formed of an outer member 2 and aninner member 3, the outer member 2 including a knuckle flange 2 e andthe inner member 3 including a hub race 31 and an inner race 32 fittedto the hub race 31; however, the present invention is not limitedthereto. For example, the wheel bearing device 1 may have a secondgeneration structure formed of an outer member and an inner member, theouter member including a knuckle flange and the inner member formed of apair of inner races; and the inner member is fitted to an outercircumference of a hub race. Alternatively, the wheel bearing device 1may have a fourth generation structure formed of an outer member and aninner member, the outer member including a knuckle flange and the innermember as an assembly where a hub race and a universal joint are fittedto each other.

Lastly, it is to be understood that the foregoing embodiments are merelyillustrative, and not restrictive, of the invention according to thisapplication; therefore, various changes and modifications may be madewithout departing from the scope of the present invention. The scope ofthe present invention is defined by the appended claims and is intendedto embrace all changes and modifications within the meanings and scopesequivalent to the claims.

REFERENCE SIGNS LIST

-   -   1 wheel bearing device    -   2 outer member    -   2 c outer raceway face    -   2 d outer raceway face    -   3 inner member    -   31 hub race    -   32 inner race    -   3 b spline hole    -   3 c inner raceway face    -   3 d inner raceway face    -   3 h through hole    -   3G guide groove    -   3R recess    -   3P projection    -   3 s side face    -   3 t upper face    -   4 rolling element row    -   41 rolling element    -   42 retainer    -   7 forming broach    -   8 finishing broach    -   8G guide plate    -   8 s cross-sectional face

1. A wheel bearing device comprising: an outer member including an outerraceway face that is formed on an inner circumference of the outermember; an inner member including an inner raceway face that is formedon an outer circumference of the inner member; and a plurality ofrolling elements that are interposed between the outer raceway face ofthe outer member and the inner raceway face of the inner member, thewheel bearing device further comprising a spline hole that is formed ina through hole of the inner member, wherein the spline hole includes aguide groove that is formed on an inner circumference of the splinehole, the guide groove through which a guide plate of a finishing broachis to be run, wherein the guide groove is formed by removing aprojection between a plurality of recesses, and wherein a hardened layerand a non-hardened layer are formed in a side surface of the guidegroove.
 2. The wheel bearing device according to claim 1, wherein theguide groove is formed of a plurality of recesses that are adjacent toeach other and are circumferentially connected to each other, theplurality of recesses being a part of recesses that form an unevenshape.
 3. The wheel bearing device according to claim 1, wherein theinner member includes a phase matching portion that is formed on aninner-side end face of the inner member and recessed at an outer side ofthe inner member, and the phase matching portion is formed in a shapewhere an inner-side opening end of the guide groove spreads radiallyoutward.
 4. The wheel bearing device according to claim 1, wherein theguide plate includes a cross-sectional face that is formed to beinclined toward a side face of the guide groove, and as the guide plategoes into the guide groove, a gap between the cross-sectional face ofthe guide plate and the side face of the guide groove is graduallyreduced.
 5. The wheel bearing device according to claim 1, wherein thedepth of the hardened layer changes such that the hardened layer has awave-shape.